1. Field of the Invention
The present invention relates to the technical field of a node device or the like included in an information communication system which has a plurality of node devices capable of performing communication with each other via a network, and in which a plurality of pieces of common information shared by the plurality of node devices are stored so as to be spread to the plurality of node devices:
2. Discussion of the Related Art
In recent years, an information communication system in which various content such as music and movies is transmitted/received among node devices belonging to a network is actively studied and developed. The information communication system is, for example, a P2P type information communication system in which content is spread to a plurality of node devices and commonly used by the plurality of node devices. Attention is being paid to the P2P-type system as a method of solving concentration of accesses to a server and high management cost as drawbacks of a conventional client-server-type model.
In a peer-to-peer information communication system, for example, in an overlay network logically constructed by using a distributed hash table (hereinbelow, called DHT), each of node devices does not recognize link information (such as destination information) to all of the node devices participating in the overlay network but has, in its RAM (Random Access Memory), as table information, only link information to node devices as a part of the node devices obtained from a contact node device or the like which is accessed first at the time of participating in the overlay network. At the time of inquiring data or the like, a CPU directly accesses the RAM to refer to the table information. Patent documents 1 and 2 disclose techniques using a DHT.
The plurality of pieces of content are stored so as to be spread to the node devices in the system. In addition, information on the location of each content in a node device is also spread and managed as cache information by the node devices.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-99337    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2003-216521